Conventional oil booms normally comprise an elongate buoyant body having an upstanding shield, and possibly also a depending, oil-confining skirt. These booms are normally stored on land in a collapsed state. The task of laying out the boom, in order to contain an oil slick, is both tedious and difficult, especially in bad weather. Alternatively, the boom can be stored afloat on the water, in a ready-to-use state, although in this case the booms are liable to present an obstacle to the normal water traffic, and also spoil the surrounding scenery. Such booms are not suited for the permanent protection of, for example, inlets which are sensitive from an environmental aspect and which lie adjacent a channel for oil tankers. Furthermore, if it is found desirable to place temporary booms around an oil tanker when unloading or loading said tanker, the booms must be laid out and taken in respectively each time it is decided to use the boom. Another disadvantage with protective booms of this kind is that when the wind blows hard, the booms are tilted by the wind, causing the efficiency of the boom to be reduced.